The basic objective of this research program is to develop specific information about the molecular basis for the mutagenicity and carcinogenicity of cyclopenta(cd)pyrene (CPP), a polycyclic aromatic hydrocarbon without a bay region. We propose to identify the metabolites of CPP generated by liver microsomes, by purified and reconstituted P-450 cytochrome P-450 enzymes, and by mammalian cells in culture. We will also identify the products of reaction between CPP and DNA formed in vivo and in vitro and will attempt to define the roles of specific DNA repair pathways in the conversion of CPP induced DNA damage to specific mutations.